Stevens-Johnson Syndrome

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Stevens-Johnson Syndrome

In this article

Stevens-Johnson syndrome (SJS) is an immune-complex-mediated hypersensitivity disorder. It ranges from mild skin and mucous membrane lesions to a severe, sometimes fatal systemic illness: toxic epidermal necrolysis (TEN). SJS, SJS/TEN overlap and TEN form a spectrum of severe cutaneous adverse reactions (SCAR) that can be differentiated by the degree of skin and mucous membrane involvement. They are mainly, but not always, caused by drugs. Erythema multiforme (EM) was previously considered to be a milder form of SJS without mucosal involvement; however, the clinical classification defined by Bastuji-Garin in 1993 separates EM as a clinically and aetiologically distinct disorder and has now been accepted by consensus.[1] Erythema multiforme is usually mild (EM minor), with only a few spots, which resolve quickly. The much less common but much more severe type (EM major) can be life-threatening with involvement of the mucous membranes in the mouth, the genital area and on the conjunctiva.

Classification

The classification is based on the percentage of body surface area detached.[2]

EM major

SJS

SJS/TEN overlap

TEN with spots

TENwithoutspots

Type of lesion

Typical targets

√

Atypicaltargets

Raised

√

Flat

√

√

√

Macules

Erythematous

√

Purpuric

√

√

√

Distribution of lesions

Localised

√

Widespread

√

√

√

√

Extent of epidermal detachment

<10%

<10%

10-30%

>30%

>10% sheets of epidermal detachment

Epidemiology

Over a period of 20 years, Bastuj's classification has successfully been in several large epidemiological studies (including RegiSCAR) which have provided reliable information on the incidence of SJS and TEN.[1]

Incidence is estimated at 2-3 cases/million population/year in Europe.[3]

It is much more common in individuals with HIV. (Estimated 1-2/1,000 in Canada.)[4]

Most patients are aged 10-30 but cases have been reported in children as young as 3 months.

Risk factors

The rarity of the disease has made it difficult to clearly ascertain specific risk factors among heterogeneous populations; however, the presence of particular HLA alleles has been found to be associated with SJS/TEN among particular groups - for example:

HLA B1502 and HLA B1508 among the Han Chinese have been found to be associated with SJS/TEN in reaction to carbamazepine and allopurinol respectively.

HLAb 5701 abacavir is associated with SJS/TEN among people living with HIV.

Screening for these genes among specific populations, before commencing medications, may help to avert occurrence of the disease among these groups.[5]

Use of the ALDEN (Algorithm for assessment of Drug-induced Epidermal Necrolysis) may be useful.[11]

A rapid assessment of prognosis should be made using the SCORTEN (Score for Toxic Epidermal Necrolysis) system. SCORTEN is an illness severity score which has been developed to predict the mortality rate in SJS and TEN. One point is given for each of seven criteria present at the time of admission. The seven criteria are:

Age >40.

Presence of malignancy.

Heart rate >120 beats per minute.

Initial percentage of epidermal detachment >10%.

Serum bicarbonate <20 mmol/L.

Serum urea >10 mmol/L.

Serum glucose >14 mmol/L.

Patients with a SCORTEN score of >3 should be managed in intensive care.

The use of corticosteroids is controversial due to the need to balance dampening of the aberrant immune response with poor healing and increased risk of infection. Some progress has been made with the use of pulsed systemic corticosteroids.

Some have advocated ciclosporin, cyclophosphamide, anti-TNFalpha monoclonal antibodies, plasmapheresis, haemodialysis and immunoglobulin therapy in the acute phase; however, none is considered to be standard at this time.[1]

Some reports have found early administration of high-dose intravenous immunoglobulin to be associated with increased mortality in SJS and TEN; this is, therefore, no longer recommended.[1]

The overall mortality rate is up to 10% for SJS and at least 30% for TEN. However, the mortality rate correlates with the SCORTEN score and is greater than 90% for people with a SCORTEN score of 5 or more.[2] The high mortality rate results primarily from the development of complications in the form of systemic infections and multiple organ failure.[12]

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